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Main results

2012

In 2012 several core-collapse supernovae and gamma-ray bursts were observed with the 6-meter BTA and 1-meter Zeiss telescopes of SAO RAS and some observational material under the program was obtained with the Zeiss-2000 telescope (Terskol Branch of the Institute of Astronomy of RAS).

Photometric and spectroscopic observations of the type IIp supernova SN 2009bw

Since there is a relation between some GRBs and core-collapse supernovae a question arises why we do not observe signs of SNE in all GRBs and, correspondingly, gamma-ray and X-ray emission is not detected in all SNe (J. Hjorth & J. S. Bloom 2011, chapter 9 in "Gamma-Ray Bursts", eds. C. Kouveliotou, R. A. M. J. Wijers, S. E. Woosley, Cambridge University Press, arXiv:1104.2274). Programs aimed to the study of such relations are fulfilled at BTA and other telescopes. Within the context of such study both SNe related to GRBs or X-ray flares (SN 2006aj, SN 2008D) and usual supernovae and GRBs are studied. In 2009 the type IIp supernova SN 2009bw (MR = -17.82) was observed jointly with D.Tsvetkov (SAI MSU), C. Inserra and S. Benetti (INAF, Italy). The supernova has shown the signs typical both for normal and for bright events of this type. During the photospheric phase the manifestation of elements of the CNO cycle were observed, which happened only in several other events. Velocities of hyrogen lines measured from data of spectral investigation (including those of BTA) remained sufficiently high, which can be interpreted as interaction between a supernova jet and matter surrounding a progenitor star. Similar manifestations were also observed for SN 2006aj related to the gamma-ray burst and X-ray flare GRB/XRF 060218.

SN 2009bw light curves
UV, optical and IR light curves of the supernova SN 2009bw. Ones of the earliest photometric points were obtained with the 1-meter SAO RAS telescope Zeiss-1000.

Modelling spectra of the type IIb supernova SN 2011fu

It is thought that type IIb supernovae explode from supergiants which did not lose their hydrogen envelope completely (e.g. see Pastorello et al. 2008, MNRAS, 389, 955). At early stages their spectra are equally dominated by helium and by strong hydrogen lines which become weaker afterwards. Besides, if assumptions about presence of hydrogen and helium lines in spectra of supernovae related to GRBs and XRFs are correct, then the observations of just type IIb supernovae are extremely important for understanding the nature of GRB progenitors. We fulfilled the detailed modelling of spectral lines of the supernova SN 2011fu which was observed photometrically and spectroscopically with many telescopes. Spectral observationes started in a week after detection and ended in 4 months. Evolution of temperature and velocity of expanding envelopes was traced. It was detected that continuum can be described by the temperature 6500-6700 K at early stages and ~5000 at late ones. Velocity of the pseudophotosphere (the layer over which the spectral lines are basically formed) were falling from 14000 km/s at early stages to 5000 km/s at the latest ones. The difference between velocities of the photospehre and hydrogen layer reached several thousands of km/s (velocity is proportional to distance from the center), which was also observed in other cases (SN 2006aj, SN 2008D, e.g. see Sonbas et al. 2008, Astrophys. Bulletin, 63, 244; Moskvitin et al., 2010, Astrophys. Bulletin, 65, 139). The determined values of the above parameters agree well with results obtained for other supernovae of this type. (SN 1993J, SN 2003bg, SN 2008ax).

SN2011fu spectra evolution

Spectral evolution of the supernova SN 2011fu (the gray line). Model spectra obteined with the SYNOW code are shown by the black lines (the solid line for H-alpha and the dashed one for H-beta)

2011

In 2011 several core-collapse supernovae and GRBs were observed with the 6-meter BTA and 1-meter Zeiss-1000 telescopes of SAO RAS. The observational material under our programs was also obtained with Zeiss-2000 and Zeiss-600 (Terskol Branch of Institute of Astronomy of RAS) and two 32-meter radio telescopes of Institute of Applied Astronomy of RAS).

Observations of GRB 110801A

Among all observed GRBs we can mark out especially the gamma-ray burst GRB 110801A which became 3 st. magnitudes brighter within half an hour. Its early spectrum was obtained, and later - a deep Rc-band image where near the optical transient one can see an extended object which may be the host galaxy. The object was observed in the r filter with GTC and in BVRcIc with BTA.

GRB 110801A field
The GRB 110801A field obtained with BTA+Scorpio on August 9.915, 2011 in the Rc filter with the exposiure time 2100 sec. The FWHM seeing was 1".2. The area of the GRB110801A field was enlarged. Precision of astrometric calibration was 0".7. It is noticeable that the objects looks double.
GRB110801A spectrum
Spectrum of GRB110801A optical afterglow obtained with BTA+Scortio ~ 4.5 hours after the burst.

The peculiar supernova SN2008iy

SN 2008iy is one of the most interesting supernovae studied within the scope of the project (Drake et al., ATel 1768, 2008; Mahabal et al., ATel 2010, 2009; Catelan et al., CBET 1780, 2009). Spectra obtained 5 months apart changed very few. The question about the nature of this object arises: is this a type IIn supernova of a quasar? In the light curve we observed the record-long rise of duration of about a year, and after the maximum a vary slow decrease (Miller et al., MNRAS, 404, 305, 2010). The active phase of the burst has been lasting several years already. Detection of spectral features typical for the nebular phase of a supernova would be crucial for solution of the object nature. Now, when the object is rather faint, it is possible to observe it only with large telescopes of the BTA class. Spectral and photometrical data were obtained with the 6-meter telescope of SAO RAS. The photometrical monitoring was also done with the telescope Zeiss-1000. The final stage of observation will be spectroscopy or wide-band photometry of the host galaxy of the object with the purpose of modelling spectral energy distribution and the study of its properties.

SN 2008iy spectra
Spectra of SN 2008iy obtained with BTA+Scorpio on April 23 (the black line) and September 25 (the gray line) 2009. The red shift of the object z=0.041 measured from BTA spectra agrees with data adduced in the paper by Miller et al.

The type Ic supernova SN 2009jf

We observed the late stage of the type Ic supernova SN 2009jf which is studied together with the team of the indian institute ARIES (S. B. Pandey, R. Roy, Brajesh Kumar, Brijesh Kumar). At the beginning of June we obtained direct BTA images in BVRc filters and the spectrum covering the total optical range. The practically total absence of signs of this nearby supernova was noted. This allows us starting the study of that region of the galaxy NGC 7479 where the explosion happened.

SN 2009jf
The type Ic supernova SN 2009jf in the nearby galaxy NGC 7479. The colored image is composed from BVRs images (the Zeiss-1000 telescope of SAO RAS, June 8, 2010).

2010

Nearby type II supernovae SN 2008gz SN 2008in.

Spectral evolution of SN 2008gz and SN 2008in was traced in collaboration with indian and italian participants of out international team. B, V, R, I light curves have been obtained. The bolometric light curve of SN 2008gz was compared with light curves of supernovae of the identical type - SN 2004et SN 1987A. The SN 2008gz explosion energy turned out to be comparable with the energy of SN 2004et. The lines had the PCyg profile in spectra close to maximum. They were investigated with the multiparametric code SYNOW (D.Branch et al., ApJ, 566, 1005 (2002)). The modelling showed that the code limitations are strong for late spectra: the emission part of hydrogen lines is described badly. To build the curves of SN 2008gz envelopes and photosphere velocity decrease the absorption minimums were measured. All details of the study of SN 2008gz are presented in the paper by R.Roy et al.

SN 2008gz
SN 2008gz spectrum obtained on November 11, 2008, with the telescope TNG+DOLORES (the thick gray line). The thin black line shows the best fitting by the model spectra generated by the SYNOW code.

The cosmological peculiar type Ic supernova SN 2009de

SN 2009de was discovered in the CRTS survey and investigated photometrically and spectroscopically at the telescopes of this survey and at Palomar 60, Palomar 200, BTA, Zeiss-1000 and Keck I. The study of such objects is important for cosmplogical tasks. To detect and study spectral energy distribution of the host galaxy of this supernova, the deep BTA imaging is planned for the nearest future. At the moment, from results of observations with BTA and Zeiss-1000 it is known that the galaxy luminosity R ~ 24.4. The KeckI noisy spectrum showed the presence of emission lines H-beta, [OIII] 4958, 5006AA, H-alpha. This means that it is possible to obtain high-quality photometrical BTA data for modelling spectral energy distribution of the host galaxy. The red shift estimation z=0.311 is close to the value determined from the fitting of wide spectral details of the SN with the SNID code.

SN2009de
Identification of emission lines of the host galaxy in the BTA spectrum of SN 2009de. The lines of [OII] 3727A, H-beta, [OIII] 4959, 5007AA were identified. The signs of the H-alpha line were recently confirmed by the KeckI spectrum of the host galaxy (A.Drake, private comm., 2010).

2009

Identification and early spectral observations of the optical transient of GRB090726

Information on the gamma-ray burst GRB090726 was got in SAO from the space platform SWIFT (the error area of radius 3) at 22:42:27 UT on 26 July 2009. The first images were obtained in BVRI bands of the Zeiss-1000 telescope of SAO RAS half an hour after the burst (Fig.1). A fading object of st.magn. 18.26 in the R band was detected within the errors of coordinate determination which was absent from DSS images. More precise coordinates received from the X-ray telescope SWIFT/XRT coincided with our data. The spectrum of the optical transient was obtained with the telescope BTA+SCORPIO in one and a half hour after the burst (Fig.2).

GRB090726
Fig.1 Left: DSS image of the SWIFT/BAT error region (the R band). Right: the direct image obtained with the SAO RAS telescope Zeiss-1000 half of hour after the gamma-ray burst. The position of the optical transient of GRB090726 is marked
GRB090726 
spectrum
Spectrum of the GRB090726 optical transient with identified lines obtained with BTA in half and an hour after the burst.

The first telegram (http://gcn.gsfc.nasa.gov/gcn3/9709.gcn3) confirming the variable character of the detected optical source was published several hours after the event. The second telegram with the results of interpretation of the spectrum obtained with BTA was published during one day agter the burst. The interpretation was fulfilled together with our Spanish colleagues within the scope of the international program of the study of GRBs. Our spectrum allowed us determining the red shift z = 2.71, identifying absorption lines of highly ionized atoms and the Ly alpha line. The spectrum of the object with coordinates R.A.(J2000.0)=16:34:43.044, DEC(J2000.0)=+72:53:04.82 was obtained with BTA - the most northern large telescope.

T.Fatkhullin, A.Moskvitin, A.Valeev, S.Fabrika, O.Sholukhova, V.Sokolov in collaboration with A.de Ugarte-Postigo (OAB-INAF, Italy), A.Castro-Tirado and H.Gorosabel (IAA-CSIC, Spain).

Participation of SAO in the international monitoring of the most distant gamma-ray burst with the red shift z = 8.26.

N.R. Tanvir, D.B. Fox, A. J. Levan, E. Berger, T.A.Fatkhullin, V.N. Komarova, A.S.Moskvitin, et al. "A gamma-ray burst at a redshift of z ~ 8.2" Nature, Vol. 461, 2009, p. 1254

Abstract. It is thought that gamma-ray bursts arise as a result of explosion of certain core-collapse stars, and some of them are so bright that the modern methods allows us observing them as far as up to red shifts z > 20. Up to now the largest measured red shift was z=6.96 for a galaxy emitting in Lyman-alpha. The paper informs that the gamma-ray burst GRB090423 is at the distance z~8.2. This means that massive stars were coming into existence and dying approximately 630 million years after the Big Bang. This gamma-ray burst also indicates the precise position of its host galaxy.

Spectral and photometrical monitoring of distant supernovae

In the course of joint spectral and photometrical observation under the international monitoring program the following supernovae were discovered: SN 2009bx, SN 2009cb, SN 2009db, SN 2009dy, SN 2009dw, SN 2009ew, SN 2009ji. Their brightness, color, redshift.

SN2009db spectrum
Comparison of spectrum of the supernova SN2009db with the template spectrum from the database SNID with the purpose to determine the object type and red shift.

T.A.Fatkhullin, A.S.Moskvitin, A.F.Valeev, O.I.Spiridonova, V.v.Sokolov in collaboration with R.Roy and Brajesh Kumar (ARIES, India) et al.

Study of spectral evolution of the supernova 2008gz

Within the scope of the international program, the spectral observation of the supernova 2008gz were performed to study its spectral evolution. The spectrum was modeled with the SYNOW code. Evolution of the photosphere and envelopes expansion velocity was investigated.

SN2008gz spectra
Spectra of the supernova SN2008gz obtained in the course of international monitoring.

T.A.Fatkhullin, A.S.Moskvitin in collaboration with R.Roy (ARIES, india) et al.

The supernova SN2009de

Within the framework of the international program the spectral and photometric observations of the supernova SN2009de were fulfilled to study the light curve, the spectrum evolution and to determine red shift. The spectra were modeled with the SYNOW code. The more precise estimation of red shift was obtained: z = 0.31.

SN 2009de 
spectrum
Spectrum of the supernova SN2009de with identified galactic emission lines and estimation of red shift.

T.A.Fatkhullin, A.S.Moskvitin, V.N.Komarova, in collaboration with R.roy (ARIES, India)

The supernova SN2008iy

Within the framework of the international program the spectral and photometric observations of the supernova SN2009iy were fulfilled to study the light curve, spectral evolution and to determine red shift.

SN2008iy spectrum
Spectrum of the supernova SN2008iy with narrow emission lines belonging to the supernova.

T.A.Fatkhullin, A.S.Moskvitin, V.N.Komarova

Optical study of the vicinity of the pulsar PSR J0205+6449 in 3C 58

The wide-band photometrical study was made of the vicinity of the young pulsar J0205+6449 in the supernova 3C58 remnant where an extended object was previously detected coinciding with the pulsar in coordinates. Its morphology and spectral properties allows us supposing that we detected an optical counterpart of the system of the pulsar and nebula of the pulsar wind. The publication "Optical Studies of the Vicinity of PSR J0205+6449 in 3C 58" was prepared.

PSR J0205+6449
Vicinity of PSR J0205+6449 as observed with BTA in the R band. The circle corresponds to the pulsar position from data of High Resolution Camera (HRC) of the X-ray observatory Chandra.

V.N.Komarova in collaboration with Astro Space Center (V.G.Kurt), PhTI (Yu.A.Shibanov, D.A.Zyuzin)

2008

Optical observation of an isolated neutron star.
In the framework of the international collaboration (Russia, Spain, Germany, South Africa, Chile) the event SWIFT J195509+261406 was optically observed during three days. It was discovered that this event is neither a classic gamma-ray burst, nor a black hole in a binary system, nor a microquasar. It corresponds rather to a model of an isolated neutron star with an anomalous magnetic field of ~1015 Gauss (a magnetar in its active phase). A variability of optical radiation of the soft gamma-repeater was discovered. It was shown that this event is a bridge in the luminosity scale between anomalous X-ray pulsars and faint isolated neutron stars.

2007

Stellar-wind Envelope of Massive Supernova Progenitor Star XRF060218/SN2006aj.
In the early spectra of the supernova SN2006aj related to the gamma-ray burst GRB060218, H-alpha hydrogen lines with velocities of 28000km/s and 24000km/s were found, which points to the existence of a stellar-wind envelope in the vicinity of the progenitor star. Such envelope is formed as a result of massive star's evolution and was observed during the burst as a powerful thermal component in its X-ray spectrum

2006

In February 2006 the spectra of GRB 060218/SN 2006aj (z=0.033) were obtained with the BTA. Like the case of GRB 030329/SN 2003dh (z = 0.1685), our observations turned out again among the very first spectral observations of these two nearest GRB/SN bursts. These observational results were obtained under a joint program of Instituto de Astrofisica de Andalucia (Alberto J. Castro-Tirado, IAA-CSIC, Spain) and SAO RAS. In 2006, the basic result of the program on identification of GRBs was formulated as follows: the long gamma-ray bursts are a beginning of an explosion of distant massive SNs. The most probably, during the gamma-ray burst we observe a relativistic collapse of a star nucleus and the birth of a very dense compact object - a supernova explosion remnant.

On April, 8, 2005, an optical afterglow of GRB050408 was discovered with SAO telescopes (the BTA and the 1-meter Zeiss). A variable object was first discovered by our observations in a gamma-ray burst localization area by the space observatory HETE. The result was considered as one of the best SAO achievements in 2005.

In 1996 we managed to see stellar-like objects (R~25) with the BTA. These were the first neutron stars (NS) that we started investigating in collaboration with the Hubble Space Telescope. We continued studying pulsar nebulae - remnants of SN bursts (PSR B1951+32 in 80), the search and investigation of optical radiation of NSs. Fluxes for the object PSR 0656+14 and Geminga were obtained with the BTA. The wide-band spectra of these NSs were built from UV to IR. The work is being fulfilled in collaboration with ASC FIAN, IKI, SAI, Mexico National Institute of Astronomy.

2005

Observations

*       GRB 050408    One of the most important achievements of SAO in 2005.

*       GRB 050509b

*       GRB 050824

*       PSR 0656+14 and Geminga

Theory

*       The cosmic gamma-ray bursts lasting more than 2 seconds (long GRBs, 2-100 sec) are now thought to be related to explosions of massive supernovae (SNe). They are idenitified in optics with very distant (host) galaxies at cosmological distances (more than 1 GPs) with red shifts about 1 (and up to z ~10). Rusults of our investigations (astro-ph/0506544) were used in modelling of energy distribution in spectra of one of such galaxies (GRB 021004, z=2.3).
      A gamma-ray burst can be accompanied with an optical afterglow lasting several days in which typical spectral and phorometric features of massive supernovae usually of types Ib or Ic are observed, as was in the case of GRB 030329 (astro-ph/0505535). In 2005 we studied a host galaxy of this (famous) GRB 030329 - a galaxy at z=0.17 with low metallicity and active star formation . Spectra and spectral energy distibution were obtained (astro-ph/0508541, astro-ph/0507488, a paper was accepted for publishing in A&A). The figure shows spectral energy distribution for a host galaxy of GRB 030329 from optical to IR.

*       In 2005 we together with researchers of the Space Reasearch Institute of RAS, Astro Space Center of RAS and Astronomical Institute of Saint-Petersburg State University studies effects of collimation of high-energy photons and other possible observational manifestations of angular and spectral distribution of photons in gamma-ray burst sources. The matter is about an alternative to relativistic fireball, if all "long" GRBs are really reltated with normal/nonpeculiar massive supernovae. Within the framework of assumptions of our model we considered effects of radiation pressure and how jets originate due to even small asymmetry of powerful radiation field in the burst source itself. Possible mechanisms of GRB origin in regions of size 10{8} cm (a compact model of gamma-ray bursts) are discussed. Observational consequencies of such "compact" energy release for GRBs are considered. (4 communications are published and submitted for publishing. A paper was accepted for publishing in "Astrofizika" journal.)

2004

Joint observational requests, in which an active participation of SAO in follow-up observations with the new specialized space platform SWIFT is supposed, are prepared and partially realized. We observed with the BTA the optical objects related with gamma-ray bursts: GRB040924 (observations of the optical transient in V, Rc and Ic filters), GRB041006 (observations of the optical transient in B, V, Rc and Ic filters), GRB041218 (the spectrum was obtained in 6 hours after the burst), GRB041219 (the spectrum of the transient in B, V, Rc filters was obtained in 2 days after the burst). New data for the GRB030329 host galaxy in V and Rc filters were obtained with the BTA.

All known results of the earliest spectroscopic and photometrical observations of gamma-ray bursts were reviewed and compared to all known earliest spectra of some massive core-collapse supernovae (SN). The summarizing of our (SAO) and other spectroscopic and photometrical data showed that the properties of early spectra/colors of optical transients of gamma-ray bursts and massive SNe are explained by a shock wave moving through stellar wind generated by the pre- supernova/pre-gamma-ray-burst. The behavior of light curves, colors and gamma-ray burst spectra (which is very similar to a ultra-violet jump observed for some SNe) is a result of dense compact envelopes near massive star-progenitors of SNe and gamma-ray bursts. The importance is emphasized of observations of namely early SNe and gamma-ray bursts spectra for understanding a crucial question in the physical mechanism of gamma-ray bursts: are ALL long gamma-ray bursts related indeed with massive SNe?

The analysis of results of the 6-meter telescope observations (+ data of observations with other instruments) shows a close relation between gamma-ray bursts and explosions of massive stars (with formation of a compact object of type of a neutron star) as a result of such an explosion. The basic principles of a compact model of the gamma-ray burst source are formulated.

2003

The earliest spectra were obtained with the BTA of an optical transient (OT) related to the gamma-ray burst GRB 030329. Typical broad details, which are already in these early spectra, point to a direct relation with a supernova (SN) burst. In the first hours the OT GRB spectrum can be a mixture of a GBR afterglow spectrum and a early UV spectrum of a massive Ib/c type SN. It could be a crucial argument in favor of an idea that a cosmic gamma-ray burst is an explosion onset of distant "massive" SNs or a collapse of massive stellar nuclei in the end of their evolution.

In 2001-2002 the effect of OT GRB 970508 reddening in several weeks after GRB was interpreted as an effect confirming the relation between long-duration GRBs and the evolution of massive stars and SN explosions, whereas nonmonotonies in the OT GRB 970508 light curve in one-three days could be a consequence of the following evolution scenario for a GRB source: "a massive star --> a WR star --> a pre-SN = a pre-GRB --> GRB and an explosion of "massive" Ib/c type SNs".

A technique of observations with a new focal reducer SCORPIO was developed. BVRI photometry of the GRB 000926 host galaxy (B=26.13) was carried out with the BTA. All objects down to a BTA-record depth of B = 27.6, V = 26.8, R = 26.8, I = 25.6 were measured photometrically in its field of dimension of ~3 arc min. By BTA/SCORPIO BVRI fluxes the photometric red shifts z were obtained for all objects and the Hubble B-diagram (B value vs. z) was plotted up to z~3.6.

Observational manifestations of different type absorption laws in GRB galaxies were studied. The modeling of energy distribution over their spectra was carried out; luminosities, ages and inner absorptions were determined; the impact of the latter on estimates of star-forming rates or SNe rate was accounted for. A question about "dark" (optically invisible) GRBs whose sources can be in highly dusty regions of galaxies was studied. A conclusion was formulated that the GRB galaxies do not differ in their spectra from other "field" galaxies, i.e. from normal galaxies of the same z. It means that we can determine an average rate of GRB observations directly from the count of these galaxies: ~5*10^{-8} GRBs per year in the Galaxy.

2002

An interpretation of the GRB 970508 reddening effect in several weeks after the burst (similar to 7 other GRBs with z<1) as an effect that directly confirms the relation between long gamma-ray bursts and the evolution of massive stars and supernova bursts. OT GRB 970508 non-homogeneities of kind of the second burst in one-three days after GRB can be a direct consequence of an evolution scenario for the gamma-ray burst source: "a massive star --> a Wolf-Rayet star --> a pre-supernova = pre-GRB --> GRB and the supernova of Ib/c type explosion".

Photometric red shifts for all extended objects with S/N>3 and "Hubble B diagrams" (relations between the stellar magnitude in B filter and z) were constructed for the objects with the red shifts about 3 in the field of the gamma-ray burst GRB 000926 host galaxy in four (BVRI) fluxes measured with the BTA/SCORPIO. Both the host galaxies (with spectroscopic z) and field galaxies obey well the Hubble general dependence for distant objects. Observational manifestations of different types of internal extinction laws in the gamma-ray burst host galaxies were studied. By the results of photometric z estimations in the field of GRB 000926 the galaxies-candidates were selected in the spectra of which an absorption line at the wavelength of 2175\AA (the absorption line of graphite dust) can present. A review of data on optical photometry and spectroscopy of all gamma-ray burst host galaxies known by the end of 2002 (including spectra with continuum of GRB optical transients) was also made. The results are presented in the form of the Hubble R diagram.

The field of OT GRB 021004 was investigated at the BTA with the SCORPIO device on the 29th, 30th of November and the 5th of December. An extended object (a blue host galaxy of gamma-ray burst with B=24.55, V=24.35, Rc=24.36, Ic=23.79) was detected which coincides with the position of an Optical transient (OT GRB) of this burst observed in October 2002.

2001

According to energy distribution in spectra obtained in BTA observations, the gamma-ray burst host galaxies do not differ from ordinary “field” galaxies of similar stellar magnitudes and red shifts. It allows us to determine an average year rate of gamma-ray bursts directly from observations.

2000

By data, obtained in BTA observations, we measured the red shift Z=0.7063 ± 0.0017 of a distant galaxy of 24th st. magn., in which there occurred a burst of a massive star accompanied by the gamma-ray burst GRB 991208. The evolution of a corresponding variable optical source was watched.

In cooperation with Space Science Institute (USA) and Astrophysical Institute of Andalucia (Spain).

1998

During a year the program on search for host galaxies of gamma-ray bursts has been carried out at the BTA. Blue compact sources were discovered in the area of optical transients GRB 970508 and GRB 980703. The identification of GRB 980519 with the today’s most distant host galaxy was fulfilled.

1997

As a result of BTA simultaneous 4-band observations we obtained the most detailed light curve of an optical stellar-like source corresponding to the gamma-ray burst of May, 8, 1997. The slope of continuous spectrum was measured in maximum and after it. The variability of colors has been watched up to 200 days after the gamma-ray burst. The brightness fall rate and the color indexes were changing. The effect of a sharp rate deceleration is noticeable in infrared (~8000A) in 36 days after the burst. These new facts affect essentially the modern notion of physical nature of gamma-ray bursts. Perhaps we observe a formation of a nebula related to the outburst in the moment of gamma-ray burst caused by the activity of a compact object of type of a neutron star.

1996

The BVRI CCD photometry of the pulsar PSR 0656+14 was carried out with BTA. By VLA radio source location a stellar-like object was identified. The flux in R and I bands were first determined what allowed us (taking into account the UV observations with HST) to speak confidently about essentially non-thermal nature of radiation in UV spectral optical part up to ~8000A. The optical spectrum can be presented as a sum of non-thermal spectrum of atmosphere (surface) of a neutron star and a non-thermal component (power-law spectrum with the index of about -0.85).

(In cooperation with Astro-Space Center of PhIAS and Penn State University, USA).

1994

Deep CCD images of the localization areas of bright gamma-ray bursts GRB 790418 and GRB 790613 were first obtained. In both cases a faint blue stellar-like object (V=24.5m, B-V < 0m) was discovered in the gamma-ray bursts localization areas. The observed brightness and colors allows us to suppose that it can be objects of type of neutron stars at distance of about 40 pc.

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Last update: 15.02.2014